In the field of cosmetic devices, there are known devices of this type in which the liquid cosmetic composition comprises a liquid phase and solid particles such as pearlescent agents that may or may not be responsive to a magnetic field, the cosmetic composition being intended to be applied to the eyelashes, lips, nails, hair, or skin of a user.
Generally, when the solid particles are responsive to a magnetic field, then the applicator comprises a magnetic applicator head to enable better loading of the applicator head and/or to orient the solid particles to provide optical effects when the composition is applied, as described for example in patent FR 2,947,432 A1 in the name of the Applicant. Other devices comprise a magnet separate from the applicator as the magnetic part, used immediately after application of the composition to create patterns by orienting the solid particles via the effect of the magnetic field of the magnet, as described for example in patent FR 2,876,011 A1.
The case of solid particles that are not responsive to a magnetic field is more common, as this concerns a very large number of cosmetic formulations. It is widely known to use solid particles in a more or less viscous liquid composition which sometimes forms a paste, as with most mascaras for example. These solid particles are generally called “fillers” and they range from pearlescent agents to pigments, including some natural or synthetic fibers that are used to obtain various well-known effects.
However, the use of these solid particles, which may or may not be responsive to a magnetic field, encounters recurring and related technical issues concerning the maximum possible concentration of solid particles in a given composition, the possibility of being able to deposit the composition on a surface, as well as the drying out of such compositions which are typically relatively viscous and therefore particularly sensitive to this latter phenomenon.
Such compositions generally comprise at most about 10 to 15% (by weight) of solid particles. Beyond that, it becomes difficult to disperse them in a composition in a stable and homogeneous manner and to spread the composition on a surface, whether by hand or in the more difficult case by applicator where the applicator head must be sufficiently loaded with product.
In practice, if one wants to have a homogeneous composition comprising solid particles that remain stable because they have very little or no mobility in the composition and/or if one wants to use a higher concentration of solid particles, it must be possible to increase the viscosity of the composition.
To do so, thickeners are generally added to try to obtain the desired viscosity for a given composition.
If the viscosity of the composition is not correctly adjusted, clumps of solid particles will form when it is too high or the particles will settle to the bottom of the container when it is too low. If the formula is too thick, it becomes difficult to load the applicator head and spread the product. It is well known to consumers of cosmetics, particularly mascara, that it soon becomes necessary to use the applicator, particularly the stem and the applicator head, as an agitator the user moves back and forth within the container to render the composition more fluid for loading onto the applicator head. This practice is not without impact on the properties of the composition because it dries more quickly when in contact with the air, which causes its viscosity to increase more rapidly.
With use, it thus becomes more and more difficult, and eventually impossible, to maintain an optimal load of product containing solid particles on the applicator head. In the case of mascara, a significant percentage of the originally provided product becomes unusable and therefore lost.